How can we check to know precisely how many UFT licences we have? Is there any software that would allow to check it?

The ability to see the license details is a feature built into the Autopass License Server. Since you said you use concurrent licenses, you will have Autopass installed. Please see page 71 in the Autopass License Server User's Guide (which I am uploading to the case for you) and you will go to the License Management section in the guide. You can look at the License Usage Report and the License Usage Pane for details on how to view all of the license information you are looking for.

You will need to have a login for the Autopass License Server. If you do not have one, you will need to have one set up fo you by your Autopass License admin. You can find out more details about this starting on page 51 about user management.